The present invention relates to pumps and pertains particularly to method and apparatus for pumping large solid articles.
Rotary disc pumps have been known for a considerable length of time. Such pumps, however, have not gained widespread use because they have been unable in the past to complete effectively with positive displacement pumps and bladed impeller pumps for the pumping of fluids.
The rotary disc pumps typically employ a multiplicity of closely spaced flat plain discs rotating within the pump housing. The pumping effect is obtained by frictional and shear forces developed between the rotating discs and the fluid. It has always been considered necessary that the discs be closely spaced in order to be effective. The prior art is exemplified by the following prior art references:
U.S. Pat. No. 1,061,142, issued May 16, 1919 to No. Tesla.
U.S. Pat. No. 2,087,834, issued July 20, 1937 to Brown et al.
U.S. Pat. No. 3,487,784, issued Jan. 6, 1970 to Rafferty et al.
U.S. Pat. No. 3,644,051, issued Feb. 22, 1972 to Schapiro.
U.S. Pat. No. 4,025,225, issued May 24, 1977 to Durant.
Other patents of interest include British Specification No. 179,043, dated May 4, 1922 to N. Tesla, and
French Pat. Specification No. 866,706, issued May 31, 1941 to Girodin.
These pumps are all based on the theory that friction of the fluid on the surface of the plates of the rotor during rotation of the rotor develops centrifugal force, propelling the fluid outward toward the periphery of the plates. These, however, recognize the necessity for maintaining a fairly close spacing between the adjacent discs. The Rafferty patent, cited above, U.S. Pat. No. 3,487,784, suggests the use of a special disc-type pump for pumping blood. It also recognizes that for pumping blood, in order to avoid high forces on the blood, the spacing between the discs should be not less than 1/4 of an inch. He does not, however, recognize the ability of the pump to function with a greater spacing or to pump solid articles.
The pumping of coal slurries and similar materials has been carried out in the past with bladed impeller type pumps. Such pumps, however, under these conditions are subjected to a very high wear rate and therefore have a very short life. They are also subject to frequent stoppage due to plugging.
The applicant has discovered the ability of the disc pump to function with a greater spacing between the discs. He has also discovered that such pumps can be utilized for pumping of fragile articles. This has subsequently led to the discovery that the pump can also handle large solid articles in a fluid medium so long as the articles can be maintained suspended within the medium. The applicant has demonstrated the pumping of solid articles, such as marbles and gravel, for example. These have been pumped at heights of 15 feet above the pump outlet with no apparent damage to the pump or to the article. Similarly, live fish and other articles have also been pumped.
It is therefore desirable that a pump be available which is capable of effectively conveying large solid articles in a fluid medium at a reasonable pressure head for a reasonable distance.